1. Field of the Invention
The present invention relates generally to a double-walled dispenser container which is free of a discharge opening and is pressure-tight. More particularly, the present invention which is used for the delivery of flowable products, especially cosmetic products, comprises a one-piece flask-like outside container and a compressible inside container. A method for manufacture of the subject container is also described.
Containers of the aforementioned type are most preferred by the cosmetic and material industries, in which pressure-resistant spray cans and dispensers are called for in ever greater measure, for packaging their liquid, soft paste, cream or gel products. Containers in which the propellent gas is separated from the filler material are very important today for various reasons. On the one hand, the propellent gases used traditionally in aerosol containers, which are generally flammable, for instance, butane, propane, etc., do not leak out to the outside with these tight containers. On the other hand such containers now also allow the use of propellent gases which in contact would chemically modify the packaged products, such as for instance compressed gases, particularly air, nitrogen, carbon dioxide, etc.
Therefore the packaging industry endeavors to manufacture pressure-tight containers which also have a long life and can still be manufactured at low cost.
2. Description of the Prior Art
Double-walled containers as they are already known from U.S. Pat. No. 4,308,973 and European Patent A-017,147, consist of a container and a cover, in which the container is essentially composed of a cylindrically shaped outer wall with an inserted inner wall having a discharge opening built onto these container parts, which supports the cover or respectively the valve attachment. Traditionally, the cylindrically shaped outer wall is manufactured of tin plate or aluminum, while the inner wall is aluminum or plastic. Aluminum or tin plate can also be used for the cover or respectively the valve attachment. It is to be understood that a container constructed in this manner can be manufactured and maintained only at considerable cost.
However it has been shown that the container constructed in three parts does not remain pressure-tight over a long period and its constancy of performance is insufficient after long use. These sealing problems are principally inherent in this type of product and arise from the mode of construction of these containers, in which the outside container is flanged over and subsequently beaded together with the inside container and the discharge opening on its opening edge. This type of joining of different solid materials cannot in a satisfactory manner withstand the increased stress of a container of, for instance 250 ml or more, which is under pressure. The counterflow movement of the different solid materials because of the edge beading or sealing leads to nonuniform regions in the joining materials in this area.
Another container has also already been made known in which the traditional discharge opening part and the cylindrical outside wall part are replaced by a one-piece outside container, in which the inside container has a collar which rests on the rolled edge of this outside container and is fastened there only upon setting and clamping of the valve cover. For the same reasons earlier mentioned, this construction cannot overcome the aforementioned sealing problems and it also gives rise to certain technical manufacturing drawbacks. The inside container must be deformed and be forced through the small container opening provided for the valve cover. Not only is this procedure costly, but also the inside container can become damaged, which need not be discussed in any greater detail at this point.
A double-walled container in which the inside container and the outside container are pushed together one into the other without deformation is also known, wherein the two edges are joined and are drawn in and beaded together. The drawing together, including the tapering of both of the cylindrical container parts, however, is possible only with use of expensive and particularly accident-causing tools. Thus, the beading of the joined points leads to technical difficulties and sets extraordinary conditions on the method for manufacture of such two-part containers.